The present invention relates generally to the image display systems. More particularly, this invention relates to an improved light delivery and distribution module with polarization conversion in the illumination system of a LCD projector implemented with or without micro lens that can be manufactured with compact size without requiring extra optical elements.
Current state of the arts in designing and assembling image delivery modules suitable for implementation in different image display system are confronted with several technical limitations. Specifically, a LCD panel display system may require different size of image sizes depending on particular LCD panel designs. Typically, the image delivery module for each different type of LCD panel display has to be individually designed such that compatibility can be achieved. Such limitation often increases the cost of design and manufacture and often leads to lower productivity and poorer product reliability due to more complicate processes are necessary in each of these production cycles.
The limitation can be understood by examining a prior art patent issued to Itoh et. al. U.S. Pat. No. 5,986,809, entitled xe2x80x9cPolarization conversion element, polarization illuminator, display using the same illuminator, and projection type displayxe2x80x9d. This patent discloses an image illuminating device with polarization conversion. Referring to FIG. 1 for the polarizing illumination device 1 according to Itoh et al. The polarizing illuminating device includes a first optical element 200 that has a plurality of beam splitting lenses 201 faced with a plurality of condenser lenses 311 for condensing the incident beam to form a plurality of intermediate beams spatially separated from one another. Itoh et al. then applies a second optical element 300 for spatially separating each intermediate beam into two polarized beams and aligning the polarization directions of the polarized beams, thereby obtaining the same type of polarized beams. In the second optical element 300, a shading plate is placed to prevent light from directly entering a section corresponding to a reflecting plane of a polarizing separation unit array. Since the ability of separating the intermediate beam into two polarized beams is thereby enhanced, it is possible to perform conversion into the same type of polarized beams polarized in the same direction. These polarized beams with same polarization direction can be processed with high efficiency.
As that disclosed by Itoh et al. the polarizing illumination device 1 is advantageous in that randomly polarized beams emitted from the light source section 10 are converted into substantially one type of polarized beams. This is achieved by the polarized light generating device 20 that includes the first optical element 200 and the second optical element 300, and the illumination region can be illuminated uniformly with the light beams polarized in the same direction. Moreover, since the process of generating the polarized beams accompanies little loss of light, almost all the light emitted from the light source section can be directed to the illumination region, which provides extremely high light use efficiency. Furthermore, since the shading plate 370 is placed in the second optical element 300, other beams polarized in a different direction rarely mix into polarized beams of the same type for illuminating the illumination region. Therefore, when the polarizing illumination device is used as a device for illuminating a modulating device to produce a display using polarized beams for a liquid crystal device, it is possible to obviate a polarizing plate. This polarizing plate is often required to place on the side of the modulating device where the illumination light enters. Even if the polarizing plate is placed as is conventionally done, since the amount of light absorbed by the polarizing plate is extremely small, it is possible to reduce the size of a cooling device needed to minimize heat generation of the polarizing plate and the modulation device. Also, the structure of the polarizing illumination device has a beneficial effect, particularly in adopting a light source for emitting light beams having low parallelism in the apparatus.
Even with so many advantages as discussed above, Itoh""s invention however suffers from the limitation that the size of the image source is fixed. The image source of fixed size can be quite limiting for compatibly adapting to application in different systems. One of such application may be a LCD panel with micro lenses wherein each micro lens may have a size smaller than the image source. Under that circumstance, Itoh""s image delivery module as described in the above referenced patent cannot be adapted conveniently. In order to produce a smaller image source, either a smaller image source must be used or the distance between the image source and the lens system or the LCD panel has to increase. The display systems using Itoh""s illuminating device become larger and often are inconvenient to implement for different LCD display systems. For example, FIG. 2 shows a LCD display system implemented with a light distribution module of Itoh. The LCD display system is implemented without the micro lenses due to the size of the image source.
Therefore, a need still exists in the art to provide an new and improved image delivery module to allow for flexible adjustment of the size of the image source. The flexibility to adjust the image source allows broader applications with requiring a longer optical path and larger volume when implemented for different image display systems. A compact and more economical application with simple design and configuration can therefore be achieved when flexibility adjusting the size of image source is provided.
It is therefore an object of the present invention to provide an image delivery and polarization conversion system with improved design and configuration for flexibly adjusting the size of the image to overcome the aforementioned difficulties and limitations in the prior art.
Specifically, it is an object of the present invention to provide a new and improved image delivery and polarization conversion device by first converting the light source image beam into uniformed polarized beams and flexibly adjusting the size of the image source by either reducing or magnifying the image source. In a particular implementation the image source is focused and reduced to an array of condenser lenses for producing image suitable for implementing a display system with LCD panel either with or with micro-lenses.
Another object of this invention is provide new and improved image delivery system with polarization conversion and image source size adjustment without requiring to use specially designed optical or control mechanism such that the implementation may be realized economically at a low cost.
Another object of this invention is provide new and improved image delivery system with polarization conversion and image source size adjustment such that compact and reliable image display system can be conveniently and economically provided with sufficient flexibility with an universal adaptable and compatible image delivery module of this invention.
Briefly, in a preferred embodiment, the present invention includes a light distribution module adaptable to a LCD display system. The light distribution system includes a first lens array having a plurality of lenses for condensing a light beam into a plurality of polarization separation elements for separating converting the light beam into a first set and a second set of uniformly polarized and mutually orthogonal beams. The light distribution system further includes a image source size reduction means for reducing a size and focusing the first set and second set of uniformly polarized beams into a second lens array having twice as many lenses as the first lens array. The second lens array has a first set of lens array for receiving the light beams with a first polarization and a second set of lenses for receiving the light beams with a second polarization orthogonal to the first polarization. The lenses of the second set of lenses further have a half plate for converting the second polarization into the first polarization thus producing a plurality of beams all with the first polarization. The size-reduced and uniformly polarized beams are ready to project through another focusing lens to a LCD panel for image display.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various drawing figures.